^ Right-click on the desktop, go to gadgets, it opens a window with all the gadgets, if you look bottom right, there should be a "get more gadgets online" link. The moon is a separate gadget by the way. Enjoy!

Edit: Found the original link, which is here: Wallpaper Link. I didn't see any other MLP images on that page, though.
Edit again: But, when you click on the title of that entry, it shows two other related MLP wallpapers, and they're both pretty awesome!